<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #box{
            width: 704px;
            background-color: #e8e8e8;
            display: flex;
            flex-wrap: wrap;
            position: relative;
        }
        #box div{
            width: 40px;
            height: 42.5px;
            margin: 2px 2px;
            background-color: #666;
        }
    </style>
</head>
<body>
    <div id="box">

    </div>

    <script>
        let oBox = document.getElementById("box");
        for(let i = 0;i < 8;i++){
            for(let j = 0;j < 16;j++){
                oBox.innerHTML += `<div style="background:url(../images/football.jpg) ${j*-40}px ${i*-42.5}px"></div>`
            }
        }

        for(let i = 0;i < 8;i++){
            for(let j = 0;j < 16;j++){
                oBox.innerHTML += `<div class="hide" style="background: #999;position:absolute;left:${j*40+j*4}px;top:${i*42.5+i*4}px;opacity:0.6;"></div>`
            }
        }
        
        let aHide = oBox.getElementsByClassName("hide");
        for(let i = 0;i < aHide.length;i++){
            aHide[i].onmouseover = function(){
                aHide[i].style.display = 'none';
            }
        }
    </script>
</body>
</html>